1. Field of the Invention
The present invention relates to a method for highlighting a region of an image displayed on a display screen, particularly when such display screen displays individually selected image elements in two levels of brightness.
2. The Prior Art
It is frequently desirable to mark a region of an image appearing on a display screen, or a text of a character appearing thereon, in order to designate the boundaries of a region which is to be manipulated in some manner. The manipulation may involve text processing or editing, for example, or may involve the erasure, displacement, enlargement, reduction or copying of specific regions.
In the past, it has been known to mark a position such as may be occupied by a character of text, with a periodic change of brightness, so that the position of the character is emphasized. In graphics picture screens, such as the Tektronix 4014 Memory Picture Screen, the position of a specific point may be identified by a graticule. In the Tektronix 4016-1, a point may be indicated by the lower left corner of the lighted rectangular region. Both of these highlighting methods have the disadvantage that part of the image is obliterated, or sometimes the graticule or the rectangle is rendered invisible, depending on the character of the image being displayed.